The present invention relates to a liquid crystal display device (both-side liquid crystal display device) of the type which is typically mounted on a foldable type mobile phone or the like and is provided with a main liquid crystal display panel and a sub liquid crystal display panel having the screen smaller than a screen of the main liquid crystal display panel; and, more particularly, the invention relates to a liquid crystal display device of this type in which the generation of brightness irregularities on the screen of the main liquid crystal display panel can be suppressed.
Along with the down-sizing of a mobile phone or a personal digital assistant, which is provided with a liquid crystal display panel, a mobile phone or a personal digital assistant which is designed such that a key pad portion and a liquid crystal display panel are folded so as to be overlapped relative to each other at the time of non-calling (at the standby time) has been commercialized. Further, in recent years, a miniaturized panel, which can display information even in a state in which the mobile phone or the personal digital assistant is folded (non-calling state), and is arranged on a back surface side of the above-mentioned liquid crystal display panel, has been commercialized.
As a liquid crystal display device (a liquid crystal display module), which includes a second liquid crystal display panel (also referred to as a sub liquid crystal display panel or a sub panel) in addition to a conventional liquid crystal display panel (also referred to as a main liquid crystal display panel, a main panel), and which is preferably used as a mobile phone or a personal digital assistant, there has been developed a product referred to as a both-side liquid crystal display device, which has two liquid crystal display panels disposed on opposite sides of one lighting system (also referred to as a backlight system), whereby the lighting device radiates light to the respective liquid crystal display panels. Such a both-side liquid crystal display device and a mobile phone on which the both-side liquid crystal display device is mounted are described in Japanese Patent Publication 2002-287144 (patent literature 1), for example.
On the other hand, a lighting device (a both-surface light-emitting flat type light source device) which radiates light respectively from both surfaces has been proposed (Japanese Patent 3326854 (patent literature 2)). Further, one example of a light guide plate (also referred to as a light guide body, a light guide), which is suitably adopted for designing an optical system of a flat light source device, is disclosed in Japanese Patent Publication 2000-310777 (patent literature 3).